When I started in this hobby 3-4 years ago I had an outbreak of Ich in my 72 gallon reef. I tried several bottled treatments, cleaner shrimp, garlic feeding...got some control but no 'cure'. It was a PIA, but I did get a QT tank, cycled it, performed hyposalinity and left the DT fallow for 6 weeks. In the long run (3+) years I am happier and I believe (who really knows) my tank inhabitants are happier as well.
Just my approach after other things failed.